Superheater for scotch boilers



Patented pr. 29, 1941 UNITED STATES PATENT QFFECE SUPERHEATER FR SCOTCH BOHLERS Application February 21, 1939,- Serial No. 257,588

1 Claim.

Our invention relates to marine superheater heat.

One form of boiler in common use in marine service at present is the so-called Scotch type having an outer cylindrical shell with internal furnace iiues leading to a smoke chamber from which return smoke tubes extend forwardly through the water space of the boiler to the smoke box and stack. In some installations in order to provide a high degree of superheat it has been customary to mount the superheater in the smoke chamber in the path of gases owlng from the furnace flues through the smoke chamber to the return smoke tubes. While this type of superheater installation has given relatively high superheat, it has suifered from the diiiiculty that it is apt to be damaged by overheating, particularly during the period of firing up the boiler.

In accordance with the present invention the superheating surface is mounted in the smoke chamber but so arranged that by controlling the firing of the several furnaces the degree of superheat may be regulated and the danger to the superheater during firing up periods is lessened.

The novel features of our invention are pointed out in the appended claim. The invention itself together with its objects and advantages will thus be understood from the following detailed description and its accompanying drawing of a superheater boiler exemplifying the invention.

In the drawing, Fig. 1 is a horizontal sectional View of part of a Scotch-type boiler embodying the invention as viewed on the line l-I in Fig. 3;

Fig. 2 is a vertical sectional view through one of the furnace flues of a boiler of this type as viewed on line 2 2 in Fig. 3; and

Fig. 3 is in part a sectional view and in part an end View with the casing removed to show details oi construction as viewed on the line 3-3 of Fig. 1.

The boiier illustrated in the drawing has an outer cylindrical shell II and three internal furnace flues I2, i3 and I4 extending through the water space of the boiler and communicating at; their rear ends with a single smoke chamber I5. The gases from all of the furnace iiues discharge into this common smoke chamber and exit therefrom through groups of return smoke tubes IEa, Ib and ISC appurtenant to the furnaces I2, I3 and I4, respectively. The rear wall of the smoke box is lined with water tubes I1 connected between drums or headers I8 and CFI 2B, the former being in communication with the Water space of the boiler by means of the water legs 2| and the latter being connected to the steam and water space of the boiler by means of the tubes 22.

The superheater inlet and outlet headers, designated as a whole by the numeral 23, are located outside of the smoke chamber I5 and the superheater tubes extend through the top of the chamber into the interior thereof. Some of the superheater tubes 24 are arranged in contacting relation in vertical rows extending longitudinally of the boiler between the central furnace iiue I3 and the furnace fiues I2 and I4 at each side thereof. Other superheating tubes 25y extend downwardly into the smoke chamber in such positions as to be located in the path of the gases flowing from the furnace ues I2 and I4 to the return smoke tubes Ilia and ISc which are located above these flues.

'I'he rows of superheater tubes 24 in eect divide the smoke chamber into three parts so that the gases issuing from the several flues pass to the smoke box and stack through return smoke tubes appurtenant to each chamber without any substantial intermingling of the gases. The gases exiting from the centrally located chamber I3 give up superheat for heating purposes mainly byvradiation to the tubes 24 since there are no superheating tubes over which these gases pass in their path from the flue to the return tubes Ib.

When a high degree of superheat is required, all of the furnaces may be fired intensely. When a low degree of superheat is required, the firing for the furnace flues I2 and I3 having superheater elements 25 in the path of the gases may be reduced while that in the flue I3 is increased in .order to provide the requisite heat for steam generation and yet obtain a reduction in the superheat temperature because of the fact that the superheater tubes 24 are heated mainly by radiation and there are no groups of superheater tubes in the path of gases from this furnace flue. When ring up the furnace flue I3 alone may be employed since the amount of heat imparted by gases therefrom to the superheater tubes 24 would not result in material damage to these tubes before steam becomes available.

What We claim is:

In a return tube boiler having three parallelly extending internal furnace flues, a single smoke chamber communicating with all of said flues, and a group of return tubes located above each ilue through which gases entering said chamber exit from the latter; tubular superheater elements arranged in contacting relation in vertical rows between the central one of said nues and the flue located at each side thereof, said rows extending longitudinally of said chamber for subdividing it to direct the gases from each flue to the return tubes thereabove; and other tubular superheater elements disposed in the path of gases from each of said side lues through said chamber and the appurtenant return tubes.

HOWARD C, TOWLE. JOHN A. BARNES. 

